Internal circuits of a semiconductor device using semiconductor elements, such as memory integrated circuit and logic integrated circuit in microcomputers or liquid crystal display (LCD) devices, are connected to devices external to the semiconductor device, such as a power supply, an LCD device, or various other semiconductor devices that generate control signals through terminals, which may be referred to as a pad electrode or pads. The pads include a bonding pad for connecting a circuit with a bonding wire and a bump pad for connecting a circuit with Chip On Film (COF) or Chip on Glass (COG). The pads are usually located around the outer periphery of the semiconductor device.
Not all the above mentioned pads, which include the bonding pad and the bump pad, connect the internal circuit with the external devices. For instance, a dummy pad, which is not electrically connected to the internal circuit, may be installed in order to maintain layout uniformity of the semiconductor device. The bump pad must be formed almost uniformly in a horizontal plane. Otherwise, the semiconductor device may suffer from defective connections when the semiconductor integrated circuit is mounted on a COF or a COG, because the weight of the semiconductor integrated circuit is not uniformly distributed during the connection process.
With regard to the bonding pad, while it is not required to maintain the layout uniformity of the semiconductor device, the dummy pad is often installed in order to even out the processing in the wafer process. This kind of dummy pad is not connected to the wiring or other signal line connected to the internal circuit. The dummy pad is manufactured by utilizing the top wiring layer and/or the wiring layer directly below the top wiring layer.
Although a protection circuit such as an electrostatic discharge (ESD) is typically installed between a pad and an internal circuit in order to prevent the damage caused by electrostatic discharge or some other types of damage, typically no protection circuit is installed for the dummy pad in the interest of saving space in the layout of the semiconductor device.
In order to solve the above problem, Japanese laid-open patent publication No. 11-233777 (Reference 1) discloses that the dummy terminal, i.e., a dummy pad installed adjacent to an array of input terminals, is electrically connected to a static electricity absorption line through a resistor. According to Reference 1, static electricity is attenuated by the resistor, thus preventing damage to the semiconductor device caused by electrostatic discharge.